1. Field of the Invention
The present invention relates to a system for controlling outputs of a plant, which is to be controlled, by adopting response specifying control.
2. Description of the Related Art
As a system for controlling outputs of a plant, which is to be controlled, by using response specifying control, there has been proposed, for example, a throttle valve control apparatus adapted to adjust the degree of opening of a throttle valve provided in an intake passage of an engine by using sliding mode control (Japanese Laid-Open Patent Publication No. 2002-318605).
The throttle valve control apparatus corrects a model parameter in a model equation of a throttle valve drive mechanism by an identifying error, i.e., a deviation from a model parameter reference value. This makes it possible to reduce a modeling error or disturbance influences in determining a manipulated variable of the throttle valve drive mechanism.
In making an output value of a plant follow a target output value, a difference between the output value and the target output value is produced due to two major causes, one being a change in the target output value and the other being a change in the output value caused by disturbance or the like. There has been a demand for achieving quicker convergence of a difference caused by a change in an output value and for slow convergence of a difference caused by a change in a target output value with some delay so as to stabilize the behavior of the plant.
In the aforesaid throttle valve control system, a convergent behavior for a difference between a target value and an actual value of the degree of opening of the throttle valve is determined by an arithmetic coefficient of a switching function in a sliding mode. For this reason, the convergent behavior for the difference caused by a change in a target output value and the convergent behavior for the difference caused by a change in an output value are inevitably set in an associated manner and cannot be set independently, thus failing to respond to the aforesaid demand.